Leading-in conductor



Dec. 1, 1931. w. L. MILLER LEADING-IN CONDUCTOR Filed Nov. 26, 1924WITNESSES:

, sel,

Patented Dec. 1, 1931 UNITED STATES PATENT' OFFICE WILLIAM'L. MILLER, OFPITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC &MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA LEADING-INoonnuc'ron.

Application filed November 26, 1924. Serial No. 752,365.

My invention relates to leading-in conductors for evacuated electricaldischarge devices and it has particular relation to the joint between aflexible terminal conductor and the leading-in wire which is sealed intothe glass vessel of such devices.

One object of my invention is to provide a stiffening means for the endof a flexible terminal wire in order to improve the joint between thesame and a substantially rigid conductor which is sealed into the glassvessel of an evacuated discharge device.

Another object of my invention is to provide an improved process and theresultant structure, relating to a joint between a rigid leading-inconductor, of tungsten or other material suitable for glass seals, and aflexible terminal conductor, preferably of stranded copper wire, aferrule being first clamped around the end of the flexible conductor,and the latter being then joined to the lead-in wire, preferably bypercussive welding.

More generally stated, an object of my invention is to provide a meansand method of improving the conductivity of a weld between a tungstenwire and a stranded copper wire, or other dissimilar wires, and toremove all bending stresses from the welded section.

In the accompanying drawings,

Figure 1 is a sectional view of a hot-cathode rectifier embodying myinvention,

Fig. 2 is an enlarged view, similar to Fig. 1, illustrating, in detail,thejoint between the flexible terminal conductor and the rigid conductorwhich is sealed into the glass ves- Fig. 3 is a view, similar to Fig. 2,illustrating a step in the process of making my improved conductor, and

Fig. 4 is a view, similar to Fig. 2, illustrating a modification of myinvention.

In Fig. 1, my invention is shown applied to an evacuated hot-cathoderectifier comprising a glass vessel 1 enclosing a cylinder anode 2 andan axially disposed incandescent cathode 3. The anode 2 is supportedupon a leading-in wire 4 which is sealed into a reentrant portion of theglass vessel. The cathode 3 is made of tungsten wire which is mountedbetween two leading-in wires 5 and 6 which are also sealed into are-entrant portion of the glass vessel.

In rectifiers of large capacit the leadin in wires 4, 5and 6, respectivey, are usually made of tungsten, molybdenum or other metal which sealswell into glass, and I the leadin -in wires are fairly thick, in orderto carry t e heavy currents involved. It is then necessary to join aflexible stranded copper wire 7 to the end portion of each of theleading-in wires, since the rigid tungsten or molybdenum conductors arenot well adapted for providing a direct connection with the base or anyother terminals to which the electrodes of the device are to beconnected.

Heretofore, the stranded flexible terminal wire has been soldered,brazed or welded directly to the rigid leading-in wire, and the jointbetween the two wires has been a source of trouble, on account of thedifficulty in providing a strong mechanical joint between the two wires.In manipulating the flexible copper wire, the stresses transmitted tothe joint ave been too large, with the result that the copper wire hasvery often broken off at the oint.

According to my invention, I so stiffen the end portion of the flexiblewire near the joint that the stress incident to manipulation of theflexible wire is not fully transmitted to the relatively weak point atwhich the two wires are joined together.

As shown in Fig. 2, the end portion of the stranded copper wire 7 isprovided with a cylindrical ferrule 8, of nichrome or other sheet metal,which is tightly clamped around the copper strands. The ferrule-cappedcopper wire is then welded to the rigid leading-in conductor 5 which issealed into the glass. Thus, when the copper wire 7 is bent sidewise,the ferrule 8 takes up a part of the strain and safeguards the joint. 4

The use of a ferrule for stiffenin the end portion of the flexiblecopper wire is of particular importance when making the joint betweenthe two wires by the percussive welding process. In carrying out thelast-mentioned process, the two wires are connected in a circuitincluding a source of electrical energy, such as a charged condenser,the

wires being first brought into contact, immediately separated, andthereupon moved through the path of the resulting arc to effect apercussive engagement of the molten ends. The manipulations involved inthe process of percussively welding the flexible or stranded wire 7 andthe rigid wire 5 are greatly facilitated by the use of a stiffsheetmetal ferrule surrounding the end portion of the flexibleconductor, as such a ferrule permits the welding of the two conductorsin the same manner as if the conductors were both rigid. As is wellknown, the percussive method of welding wires produces joints which areelectrically and mechanically superior to other kinds of joints, andsuch welding is very difficult and expensive to carry out with anordinary stranded, flexible conductor, owing to the tendency of theindividual strands to become excessively heated and splutter. Thestranded wire lacks, furthermore, the rigidity required in order toeffect the percussive engagement.

The use of a ferrule or sleeve on the end of the copper conductor hasthe further advantage that it prevents the copper. which has a muchlower melting point than tungsten, from melting and falling away beforethe tungsten reaches a welding temperature.

\Vhen the weld is completed, the flexible conductor and the surroundingferrule are both welded to the rigid leading-in wire in a singleoperation. I have obtained the best results when using a ferrule ofnichrome in connection with a stranded copper wire and a leading-in wireof tungsten.

In Fig. 4 is shown a modification of my invention wherein the joint madeaccording to my invention between the flexible conduci tor 7 and therigid leading-in wire 5, is fur ther strengthened by solderingadditional metal 9 around the joint of the ferrule 8 and the rigidconductor 5.

In the claims. the expression high temperature metal means eithertungsten or molybdenum.

I claim as my invention:

1. The method of uniting a copper conductor to a conductor ofhigh-temperature metal which comprises placing a nichrome sleeve aboutthe immediate end of said cop per conductor and welding said immediateend to one end of said second-named conductor.

2. The method of uniting a copper conductor to a conductor ofhigh-temperature metal which comprises placing a sleeve of materialcapable of fusing with both the copper and the high-temperature metalabout the immediate end of said copper conductor and welding saidimmediate end to one end of said second-named conductor.

3. The method of welding a stranded cop per conductor to a conductor ofhigh-temperature metal which comprises placing a nichrome sleeve aboutone end of said stranded conductor and substantially flush with saidend, bringing said end and one end of said second-named conductor to aWelding temperature, and pressing said ends together.

4. The method of welding a stranded copper conductor to a conductor ofhigh-temperature metal which comprises placing a sleeve of materialcapable of fusing with both the copper and the high-temperature metalabout one end of said stranded conductor and substantially flush withsaid end, brin ing said end and one end of said secon named conductor toa welding temperature, and pressing said ends together.

5. The method of Welding a stranded conductor to a solid conductorhaving a higher melting point than said stranded conductor whichconsists in applying a metal sleeve or ferrule about the immediate endof said stranded conductor, said sleeve having a higher melting pointthan said stranded conductor, and then welding said sleeve and saidimmediate end to one end of said solid conductor.

6. The method of welding a flexible conductor to a rigid conductorhaving a higher melting point than said flexible conductor whichcomprises placing a metal sleeve or ferrule about the immediate end ofsaid flexible conductor, said sleeve having a higher melting point thansaid flexible conductor. bringing said immediate end and one end of saidrigid conductor to a welding temperature, and then pressing said endstogether.

7. A composite body consisting of a fleze ible metallic conductor, areinforcing metallic sleeve positioned about the immediate end of saidflexible conductor, and a rigid metallic conductor having one endthereof joined by fusion to both said flexible conductor and saidsleeve.

8. A composite body consisting of a stranded metallic conductor areinforcing metallic sleeve positioned about the immediate end of saidstranded conductor, and a rigid metallic conductor having one endthereof joined by fusion to both said stranded conductor and saidsleeve.

9. A composite body consisting of a flexible metallic conductor, areinforcing metallic member positioned about the immediate end of saidflexible conductor, and a rigid metallic conductor having one endthereof joined by fusion to both said flexible conductor and saidmember.

In testimony whereof, I have hereunto subscribed my name this 18th dayof Nov.,

WILLIAM L. MILLER.

